In the electrophotographic printing process, a toner image can be fixed or fused upon a support (e.g., a paper sheet) using a fuser member or transfix member. Such fuser or transfix members often include polymer (e.g., polyimide) substrates, referred to as belts, as a support layer. In addition, fusing members and transfix members can have one or more additional polymer layers, such as release layers for providing improved release of toner; and cushioning layers for providing desired resiliency and elasticity. Materials used for belts, release layers and cushioning layers can have rigid requirements with respect to such things as modulus of elasticity, durability, onset decomposition temperature and so forth. Further, the polymeric materials from which the belts and other layers are made typically have a low thermal conductivity near room temperature, which can be undesirable.
Current efforts in electrophotographic component development are aimed at improving the physical properties and thermal conductivity of belt substrates and other polymeric fuser and/or transfix members. Additionally, efforts are also underway to improve the release properties of the surface layers of fuser and transfix members to avoid problems, such as toner offset.
Metal and ceramic fillers have been incorporated into polymeric materials to enhance thermal conductivity of fuser and transfix members. However, incorporation of metal and ceramic fillers into polymeric material can undesirably decrease the Young's modulus of polymeric material. Further, such fillers generally do not improve, and may be detrimental to, release properties of fuser surface layers. To improve release properties, fuser release oil (e.g., silicone oil, such as am inofunctional silicone oil) is often applied to the surface of fuser members during the fusing process to avoid the problem of toner offset. However, the use of such release oil increases the cost and complexity of the electrophotographic process. Additionally, amino functional release oil can chemically react with surface layers and toner ingredients, thereby initiating and/or leading to image offset failure.
Boron nitride (BN) powder is known to improve thermal conductivity for polymeric materials generally, including polyimide. However, the crystal structure of boron nitride leads to inherent anisotropy in the material and hence several physical properties, such as thermal conductivity, coefficient of expansion, refractive index, etc., are different in the a-b plane versus the c-direction. This anisotropy is most notable in thermal conductivity where the in-plane thermal conductivity (i.e. in the a-b plane) is estimated to be as high ˜300 W/mK, while the through-plane (in the c-direction) thermal conductivity is less than 10 W/mK. Due in part to the anisotropic character of BN, the effects of incorporation of the BN powder into polyimide to improve thermal conductivity have not been as significant as anticipated. For example, while BN powder is known to have increased thermal conductivity in polyimide, it does so with very high concentration (e.g., above 20%) due to its inefficiency from anisotropic conduction. In addition, boron nitride is not generally known for improving release properties in electrophotographic components, such as fusers or transfix members.
It would be desirable to provide novel polymer composite materials suitable for use in fuser belts and other electrophotographic component layers having higher thermal conductivity, high thermal diffusivity and/or a high Young's modulus. Additionally, fillers that can improve release properties of fuser and/or transfix members and/or that can allow for reduced amounts of release oil and/or and an oil-less fusing process would also be desirable.